Image-based computational fluid dynamics (CFD) has emerged as a central tool in the evaluation of hemodynamic factors in cardiovascular disease development and treatment planning, to the point where major vendors are now seeking to deploy CFD solvers on their medical imaging platforms. Detailed hemodynamic data available from CFD reveal complicated flows that are difficult to render clearly - and thus communicate to clinical stakeholders - using conventional engineering flow visualization techniques. This is especially challenging considering the four-dimensional nature of the flow patterns (i.e., varying in space and time), as well as the clinical need for generating static reports rather than cumbersome digital animations. Taking a cue from the rich history of biomedical illustration, the goal of our multi-disciplinary collaboration between the University of Toronto and the Ontario College of Art and Design University is to develop new data-driven paradigms for visualizing blood flow, based on the principles of illustration, sequential art and caricature, and informed by the visual vocabularies and conventions of radiology and vascular surgery. Our first investigations have involved the depiction of transitional flows in cerebral aneurysms. The top row of the included figure shows selected frames from an animation of vortex cores (i.e., positive and negative Q-criterion), created using the open-source scientific visualization package, Paraview. Note how difficult it is to infer the dynamics from these static images. For the bottom row, vortex cores were outlined in black to better discriminate them from each other. Surface shading was enhanced, and colouring was used to highlight selected cores, the dynamic motion of which can be followed easily across the individual frames. The original translucent lumen surface rendering was also replaced by a simple outline drawing that nevertheless retains, and perhaps even heightens, the impression of a 3D aneurysm. Although this example was composed by a professional biomedical illustrator (JH) using graphics editing tools applied to the individual static frames, we are presently working towards automating these steps in collaboration with Toronto-based Side Effects Software, developers of the Houdini 3D Animation suite widely used in the motion picture industry.